During the monsoon season, which typically lasts from July to September, the Arabian Sea warms up and causes heavy rainfall all over Pakistan. This rainfall is then channelled into the rivers and low-lying areas as floodwater. The Indus River and its tributaries in Sindh are very active during the monsoon season and, therefore, not only carry this excess water downstream, but also cause a lot of flooding in the coastal areas and on both sides of the river.
Floods in Sindh are happening more frequently and with greater intensity than before. There are multiple reasons behind this phenomenon, for instance, climate change. There has been an increase in extreme and erratic weather patterns; and it has also been recorded that the frequency of extreme precipitation events has increased in the last few decades. Extreme precipitation events occur when the amount of rain in one day exceeds the expected amount.

In Sindh, the number of extreme precipitation events are increasing every year. The second reason for increased flooding in Sindh is the increased flow of water into the province due to melting of glaciers and the flow of water into Sindh from Afghanistan, China, India and Tajikistan has also increased.

The other reasons include low and extreme land elevation, the high rate of urbanisation, poor water management practices, low-lying land, lack of river flow management, none or few flood barriers and dams, and weak governance. These are all the main reasons that the southern province of the country has been facing devastation frequently for a few years.